I am unfamiliar with Cicada Killer Wasps but did find some information through the University of Kentucky that may be helpful here:
http://www2.ca.uky.edu/entomol...
Outside of killing them by using a pyrerthroid-based insecticide at the entrance of the nest or directly in the burrow, U of K suggested that flooding the base of the plants above the burrows with water may encourage the wasps to move elsewhere.
I wish I could be more helpful. Hopefully, someone else will have suggestions?
